The present invention relates to an acoustically matched reaction resin compound for damping coating of surface wave components and to the use thereof.
Surface wave components, for example surface wave filters, are electronic components that are used to process signals of electromagnetic waves having an informational content. Depending on the components that are utilized, for example, in radar systems, television and video equipment, the signal or, respectively, the electrical pulse or current carrying the information, is converted into mechanical or, respectively, acoustic vibrations. These are referred to as surface waves.
Piezoelectric transducers are used for electro-acoustic conversion or for the generation of the surface waves. These piezoelectric transducers are constructed from defined ceramics or crystalline materials, for example lithium niobate. The acoustic properties of the piezoelectric transducer are influenced by the structure of the piezoelectric transducer. In this regard, the acoustic properties are influenced by the specific geometrical design of the "sound-generating" transducer surface. It is thereby possible to designationally modify the acoustic signal. This, for example, could allow the filtering of specific wavelength ranges out of the overall spectrum, for example the intermediate frequency of a television or video signal of about 38 MHz.
In order to prevent an undesirable echo due to the reflection of surface waves that cannot be completely converted back into electrical signals, or due to surface waves that propagate in the wrong direction, the surface of the transducer element is provided with a damping compound. The damping compound functions to absorb the energy of the surface waves. Heretofore, the damping compound, applied only in defined regions of the component such as the chip edges, has been composed of an organic material, for example a polyamide, because of the required, mechanical-dynamic properties.
There are a number of methods, through which the damping layer can be applied. For example, formed members of an extruded material can be tailored, and then are applied on the transducer surface. The members are firmly joined to the surface, through melting, in a thermal step. This step, however, must be individually performed for each component, and is involved and time-intensive. It is also known to use printing methods such as, for example, silk screening.